Aluminum stranded wires, which have electric conductor wires composed of an aluminum-based material, are used as a cable. In order that such cables are connected to various electric instruments or are connected to each other, a connection terminal is equipped at both ends of aluminum stranded wire. As the connection contact, a contact of a crimp contact-type is used.
As illustrated in FIG. 5, the crimp contact has a crimping portion 10 of a U-shaped cross-section and a bolt-fastening portion 13, and a serration 12 is provided in the inner face of the crimping portion 10, the serration 12 being formed of a plurality of concave grooves 11 for preventing the aluminum stranded wire from coming out. A hole 14, in which a bolt or the like will be pierced, is formed in the fastening portion 13.
An aluminum stranded wire (not illustrated) made naked by stripping a sheath of an aluminum cable terminal is inserted into the crimping portion 10, and side walls 15 of the crimping portion 10 are pressed from the outside, so as to crimp the portion and the wire to each other. Aluminum wires which constitute the aluminum stranded wire are fitted into the grooves 11 of the serration 12 by the crimping, so as to be prevented from coming out. Additionally, an oxide film of the aluminum wires, which constitute the aluminum stranded wire, is broken so that the metal which is inside the oxide film has exposed. Thus, good electric connection is attained.
Various improvements in connectivity between the aluminum stranded wire and the crimp contact have been proposed.
Examples thereof include: a structure in which powder of a metal, which is softer than the aluminum stranded wire, is dispersed in an inner face of a crimping portion to coagulate (adhere) the crimping portion inner face with the aluminum stranded wire; a structure in which a powder, which is harder than the aluminum stranded wire, is dispersed to break an oxide film on the surface of aluminum wires; a structure in which powders of the above softer one and harder one are dispersed; a structure in which fitting depths of serrations (grooves) are made different from each other; a structure in which a serration (groove) is formed into a spiral form; and a structure in which protrusions are formed on the inner face of a crimping portion.
However, the structures in which metal powder is dispersed or adhered have such a problem that costs and labors are required, and the above-mentioned groove structure and protrusion-formed serration form have such a problem that aging deterioration in contact resistance cannot be sufficiently prevented.